Gas dispersion measurements in mechanical flotation cells: Industrial experience in Chilean concentrators

This technical note presents results of gas dispersion measurements carried out in industrial mechanical flotation cells from Chilean concentrators. Results showed that superficial gas rate, gas holdup and bubble size were within ranges found in literature. The bubble surface area fluxes (SB) were computed using the superficial gas rates and the Sauter mean diameters, obtaining approximate SB ranges from 20 m2/s/m2 to 60 m2/s/m2 for both self-aerated and forced-air flotation cells. Despite the different cell types, sizes and wide range of operating conditions, an exponential relationship between superficial gas rate (JG) and Sauter mean diameter (D32) was obtained: D 32 = D 0 · e γ · J G , D 0 = 0.77 ± 0.11 , γ = 0.77 ± 0.09 This result allows predicting D32 as a function of JG. Data on gas holdup (εG) as a function of Sauter mean diameter were also presented: For JG < 1.2 cm/s, gas holdup increases as superficial gas rate increases, indicating a dominant effect of superficial gas rate; for JG > 1.2 cm/s, gas holdup decreases as D32 increases, indicating a predominant effect of bubble coalescence.